Telephone metering system



Dec. 27, 1938. 'H. DOHLE' 2,141,463

TELEPHONE METERING SYSTEM Fil ed Nov. 2, 1935 FIG] I ZY I a l z IINVENTOR. H/IVRICH DOHLE A TT ORNE Y.

Patented Dec. 27, 1938 PATENT OFFICE 2,141,463 TELEPHONE METERING SYSTEMHinrich Diihle, Berlin-Haselhorst, Germany, assignor' toTelephon-Apparat Fabrik E. Zwretusch & 00., Berlin, Germany ApplicationNovember 2, 1935, Serial No. 47,971 In Germany November 29, 1934 4Claims.

The subject of the present invention relates to a circuit arrangementfor call metering at a telephone subscribers station.

For the purpose of advancing the meter or .3 other charging device atthe subscribers station, switching arrangements are known in whichmetering is effected by applying to the line at the exchange a potentialwhich is higher than the normal working potential. In the cases in which1 the meter is permanently connected to the line a glow lamp isconnected between the meter and the line, the striking potential of theglow lamp being above the normal working potential of the system so thatduring the speaking condition 1.3 of the line no additional attenuationis produced by the connection of the meter to the line.

In the known arrangements in which the meter or other switching deviceis permanently connected to the line by way of a glow lamp, the hightension potential necessary for the operation of the glow lamp isproduced by a transformer which is arranged in series with the exchangebattery and is con-nected to a source of alternating current. If new theworking potential is less than the extinguishing potential of the glowlamp, in the known systems only a very brief impulse can be produced forinfluencing the switching arrangement, for example, the meter. Theduration of this impulse is not sufficient for many purposes in the casewhen the transformer is connected to a source of alternating currentwhose frequency is 50 cycles or more.

By the present invention impulses can be produced of any desiredduration for the purpose of influencing the device connected to the lineover the glow lamp, by using for the additional potential an alternatingcurrent source of normal frequency e, g. the lighting mains.

In small and medium sized telephone exchanges the only sources availableare the exchange battery of 60 volts, and the lighting mains, so thatthe invention may be applied with advantage in these cases. According tothe invention, the direct current potential necessary for striking andrunning the glow lamp is obtained by connecting a rectifier in serieswith the exchange battery, the rectifier being fed from a transformerconnected to the lighting mains. This arrangement has the advantage thatno potential which would endanger the telephone system can reach thetelephone lines over the rectifier.

Two embodiments of the invention are represented in the drawing;

Fig. 1 representing the arrangement for a call meter in the case of anordinary subscribers connection, and

Fig. 2 the arrangement for a call meter for use with a subscribersconnection having a feeding bridge in the exchange for feeding anextension station at the subscribers position.

In Fig. 1, N represents the subscribers telephone set which is connectedwith the exchange devices over the line a and 1). Of the exchangedevices only the metering relay Z having winding Z1 and ZII is shown.Relay Z controls the operation of the meter at the subscribers stationover contact ZIII at the appropriate time. The meter Y is connected tothe b-lead over the glow lamp G. The glow lamp G does not strike withthe 60 volt exchange battery B on the line so that the meter Y isconnected to the line during speaking conditions without any dampingeffect.

In order to produce the necessary striking potential for the glow lamp Gthe exchange battery B is connected in series with a rectifier bridge Grwhich is fed from the lighting mains by way of a transformer Tr. Thetransformer is so arranged that the potential obtained from thesecondary is 60 volts, so that by having the rectifier GT and the 60volts exchange battery connected in series a total potential of 120volts is produced which strikes the lamp G. It is convenient to have anadjustable resistance Wi connected in series with the rectifier bridgeand the exchange battery.

In the circuit arrangement shown in Fig. 2, in addition to the devicesmentioned in Fig. 1, a feeding bridge is connected in the exchangeconsisting in the known way of choke coils Dr2 and D1'3 and ofcondensers Cl and C2. At the subscribers extension station N a furtherchoke coil Dr! is arranged over which the feeding current flows in theknown way when the subscriber sets up an extension call.

In order to prevent the occurrence of disturbances when the meteringcurrent is connected to the line over contact 2111, an ion-hydrogenresistance W or metal filament lamp is connected in the feeding leadbetween the subscribers station and the point to which the meter isconnected thus limiting the current over the subscribers line andpreventing an undesirable fall of potential.

What is claimed is:

1. In a telephone metering system, a subscribers station and linetherefor, a call charging meter at said subscribers station, a glow lampconnecting said meter with one conductor of said line, an exchangebattery, means for connecting said battery to said line to supplytalking current for calls thereover, a full wave rectifier connected tosaidexchange battery, a transformer connected to said rectifier, asource of alternating current j connected to said transformer, and meansfor connecting said rectifier and said exchange battery in series tosaid line to strike said glow lamp and operate said meter. 7

2. In a telephone metering system, a subscribers station, an exchange,a'line connecting said station with said exchange, a glow lamp and acall meter connected together in series to said line at said station, anexchange battery to supply direct current for the normal operation ofthe telephone system and to supply talking cursaid glow lamp and operatesaid subscribers,

meter.

3. In a telephone metering system, a subscribers station, a callcharging meter at said station, an exchange, a two-conductor lineinterconnecting said station and said exchange, an exchange battery,means for connecting said exchange battery to said line to supplytalking current for calls thereover, a transformer at said exchangehaving its primary, winding connected to a source of alternatingcurrent, a full wave rectifier bridge at said exchange, a'secondarywinding on said transformerconnected to opposite sides of said rectifierbridge, said exchange battery connected to another side ofsaid rectifierbridge, a control conductor extending from the remaining side of saidrectifier bridge, and means controlled by the release of a completedtelephone connection for connecting said controlconductor to one of saidline conductors to operate said meter.

4. In a telephone metering system, a subscribers station, an. exchange,a two-conductor line interconnecting said station and said exchange,

, an exchange battery, means 'for connecting said erating said meter, asource of alternating current, a transformer having its primary windingconnected to said source, a secondary winding on said transformenacontrol conductor, means responsive to the release or" a completedtelephone connection by the subscriber at said station for connectingsaid control conductor to one of said 7 line conductors; and a fullwavelrectifi'er bridge connected to said secondary Winding, saidexchange battery, and said control conductor in such a manner that theresultant potential of direct current, flowing in the control conductorand the said one line conductor is sufficient to operate said meter.

, V HINRICH DGHLE.

